Just to be clear, I'm not suggesting that the reason these people ride on the wrong side of the road is because they are day laborers or because they do not speak English! In fact, I have wondered, many times, if the laws and/or norms in the places many day laborers come from dictate that cyclists should ride on the left side. It could be that simple, but I find it frustrating that I can't correct this behavior to help these cyclists avoid a disastrous fate.
Also, it isn't ONLY cyclists in this demographic who are guilty of this offense. I see teenagers doing it, parents with young children doing it, and even grown men and women on very expensive bikes doing it. It'll never happen, but perhaps test-based licensing for the privilege to ride certain roads might help?